You will not notice a bit of difference changing them out.
The stock banjos have what some say is a restrictive check valve. Its purpose is not really known. I did read once that they check valves were not actually a check valve per se, but they are there to stop a reversion wave that can occur in certain situations. What the reversion wave would do is actually lower the fuel pressure at the injector tops.
The way it was explained to me so that I could wrap my little pea brain about what that meant was this.
Lay on an old "full motion" waterbed. Kick your feet in tempo. If you get the right rhythm you will notice that the waves actually seem to build upon themselves without putting any more energy into your kicking. The same type of thing could occur in a certain situation in the fuel rail with the rhythm of the injector pulse.
Now, put a board under you on that waterbed and try it using that same rhythm as before. You can't get the same wave action going. That is the purpose of the valves, to change the wavelength of the fuel system.
This is pure speculation on my part as I have not heard this from anyone beyond that one person. For what its worth, I have the 6.4 banjos
installed, but I also put the updated "blue" fuel pressure regulator spring
in at the same time. My hope is, that if this speculation is correct, the additional fuel pressure I got by installing the updated fuel regulator spring would either prevent the wave or diminish its occurrence.